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Appendix -
B.3
1 POTS Advanced VoIP G.729 Service
Profile
B.3.1
Service Characteristics
¢
G.729 codec, 20msec sample interval
1 POTS
¢
T.38 Fax
¢
DSCP priority marking behind the SU is used, with the following values:
¢
¯
¯
¯
Single media stream to support Call-Waiting
¢
B.3.2
Voice RTP BW Calculation
The required bandwidth for a G.729 call (8 Kbps codec bit rate) with RTP and 20
bytes of voice payload is:
Total packet size (bytes) = (Ethernet of 18 bytes) + (IP/UDP/RTP header of 40
bytes) + (voice payload of 20 bytes) = 78 bytes
Total packet size (bits) = (78 bytes) * 8 bits per byte = 624 bits
PPS (Packets Per Second) = (8 Kbps codec bit rate) / (160 bits) = 50 pps
Note: 160 bits = 20 bytes (voice payload) * 8 bits per byte
Bandwidth per call = Total packet size (624 bits) * 50 pps = 31.2 Kbps
B.3.3
Voice RTCP BW Calculation
RTCP BW is 10% of RTP: 10 % of 31.2 Kbps is 3.12 Kbps.
B.3.4
T.38 14,400 Kbps Fax RTP BW Calculation
The required bandwidth with a 20 msec sample interval is as follows:
200
63: RTP traffic
26: RTCP and VoIP traffic
0: Data traffic
WiLink-I Modular Base Station System Manual
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